mirror of https://gitee.com/bigwinds/arangodb
88 lines
3.3 KiB
C++
88 lines
3.3 KiB
C++
////////////////////////////////////////////////////////////////////////////////
|
|
/// DISCLAIMER
|
|
///
|
|
/// Copyright 2014-2017 ArangoDB GmbH, Cologne, Germany
|
|
/// Copyright 2004-2014 triAGENS GmbH, Cologne, Germany
|
|
///
|
|
/// Licensed under the Apache License, Version 2.0 (the "License");
|
|
/// you may not use this file except in compliance with the License.
|
|
/// You may obtain a copy of the License at
|
|
///
|
|
/// http://www.apache.org/licenses/LICENSE-2.0
|
|
///
|
|
/// Unless required by applicable law or agreed to in writing, software
|
|
/// distributed under the License is distributed on an "AS IS" BASIS,
|
|
/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
/// See the License for the specific language governing permissions and
|
|
/// limitations under the License.
|
|
///
|
|
/// Copyright holder is ArangoDB GmbH, Cologne, Germany
|
|
///
|
|
/// @author Daniel H. Larkin
|
|
////////////////////////////////////////////////////////////////////////////////
|
|
|
|
#ifndef ARANGODB_CACHE_TRANSACTION_WINDOW_H
|
|
#define ARANGODB_CACHE_TRANSACTION_WINDOW_H
|
|
|
|
#include "Basics/Common.h"
|
|
#include "Basics/ReadWriteSpinLock.h"
|
|
#include "Cache/Transaction.h"
|
|
|
|
#include <stdint.h>
|
|
#include <atomic>
|
|
|
|
namespace arangodb {
|
|
namespace cache {
|
|
|
|
////////////////////////////////////////////////////////////////////////////////
|
|
/// @brief Manage global cache transactions.
|
|
///
|
|
/// Allows clients to start a transaction, end a transaction, and query an
|
|
/// identifier for the current window. If the identifier is even, there are no
|
|
/// ongoing sensitive transactions, and it is safe to store any values retrieved
|
|
/// from the backing store to transactional caches. If the identifier is odd,
|
|
/// then some values may be blacklisted by transactional caches (if they have
|
|
/// been written to the backing store in the current window).
|
|
////////////////////////////////////////////////////////////////////////////////
|
|
class TransactionManager {
|
|
public:
|
|
//////////////////////////////////////////////////////////////////////////////
|
|
/// @brief Initialize state with no open transactions.
|
|
//////////////////////////////////////////////////////////////////////////////
|
|
TransactionManager();
|
|
|
|
//////////////////////////////////////////////////////////////////////////////
|
|
/// @brief Open a new transaction.
|
|
///
|
|
/// The transaction is considered read-only if it is guaranteed not to write
|
|
/// to the backing store. A read-only transaction may, however, write to the
|
|
/// cache.
|
|
//////////////////////////////////////////////////////////////////////////////
|
|
Transaction* begin(bool readOnly);
|
|
|
|
//////////////////////////////////////////////////////////////////////////////
|
|
/// @brief Signal the end of a transaction. Deletes the passed Transaction.
|
|
//////////////////////////////////////////////////////////////////////////////
|
|
void end(Transaction* tx) noexcept;
|
|
|
|
//////////////////////////////////////////////////////////////////////////////
|
|
/// @brief Return the current window identifier.
|
|
//////////////////////////////////////////////////////////////////////////////
|
|
uint64_t term();
|
|
|
|
private:
|
|
std::atomic<uint64_t> _openReads;
|
|
std::atomic<uint64_t> _openSensitive;
|
|
std::atomic<uint64_t> _openWrites;
|
|
std::atomic<uint64_t> _term;
|
|
std::atomic<bool> _lock;
|
|
|
|
void lock();
|
|
void unlock();
|
|
};
|
|
|
|
}; // end namespace cache
|
|
}; // end namespace arangodb
|
|
|
|
#endif
|